It is generally known that vehicles with internal combustion engines can lead to environmental pollution or exhaustion of energy due to excessive consumption of energy. Thus, instead of using an internal combustion engine as a power source, vehicles using electricity as a power source (i.e., electric vehicles) and vehicles using a combination of an internal combustion engine and electricity (i.e., hybrid vehicles) have been developed and used.
In this regard, electric vehicles (EVs), hybrid electric vehicles (HEVs), fuel cell vehicles, and fuel-cell hybrid vehicles must drive using a motor with a voltage charged in a battery. Conventionally, a high-capacity charging battery has been widely used in electric vehicles, and a battery charging device for charging the high-capacity charging battery has also been embedded in the electric vehicles. Electric vehicles may include a low voltage DC-DC converter (LDC) configured to charge a battery of 12 volts (e.g., auxiliary battery), as well as to power on the entire load of the electric vehicle. The LDC can charge the 12V battery through conversion of high-voltage battery power.
The LDC operates in two modes, i.e., an operating mode and a charging mode. If the LDC operates in the operating mode, power of a main battery is supplied to the entire load of a power system so that the vehicle can operate with the battery power. If the LDC operates in the charging mode, an On-Board Charger (OBC) and a cooling fan are powered on so that it can control the charging process and can counteract excess heat emission. The OBC refers to a charging device embedded in a vehicle designed to use power as a power source. If the vehicle is charged with electricity through the OBC, an OBC control power-supply unit and a cooling fan are powered on, resulting in reduction of an output current of the LBC.
An input current sensor and an output current sensor may be simultaneously used to operate power conversion components such as the LDC or OBC, so that they can monitor input/output (I/O) signals. Recently, a method for estimating an output current using a value of the input current sensor without using the output current sensor has been widely used. As a result, although the cost and size of manufactured products are optimized, the output current sensor disappears, so that the sensing accuracy of the input current sensor becomes more significant.
Current transformers (CTs) are used to sense a current value of power conversion components installed in eco-friendly vehicles (e.g., electric vehicles, hybrid electric vehicles, etc.). In order to perform current sensing using a CT, a peripheral circuit including diodes, resistors, and capacitors are additionally needed.
An electronic component which is particularly sensitive to temperature from among a plurality of power electronic components used in the peripheral circuit is a diode. The higher the temperature, the lower the forward voltage (Vf), and the lower the temperature, the higher the forward voltage (Vf). As a result, an unexpected error may occur in the current sensing due to the diode. In order to reduce the current sensing error, there is a need to minimize the forward voltage (Vf) value of the diode affected by the temperature.